Method and product for shielding windings



April 16, 1968 N. c. TUCKER METHOD AND PRODUCT FOR SHIELDING WINDINGS Filed Jan.

INVENTOR. NOEL- C. TUCKER United States Patent M 3,378,626 METHOD AND PRODUCT FOR SHIELDING WINDINGS Noel C. Tucker, Los Angeles, Calif. (7754 Densmore Ave., Van Nuys, Calif. 91406) Filed Jan. 6, 1966, Ser. No. 532,018 9 Claims. (Cl. 17435) ABSTRACT OF THE DISCLOSURE This invention relates generally to the shielding of electrical windings and more particularly to a method and product for facilitating electrostatic shielding operations in the manufacture of shielded windings, such as employed in transformers and the like.

It is conventional practice to shield electrical windings, such as transformer windings, to avoid stray radiation, induction pickup between adjacent windings resulting in cross-talk, and undesired accumulation of electrostatic charges as a consequence of improper grounding. Normally, the shielding simply comprises a dielectric backing sheet provided with a conductive foil on one surface,

the backing sheet and foil being wrapped about a coil or winding with the backing sheet disposed between the foil and the winding turns themselves. The conductive foil serves to block stray radiation, and this foil is nor mally electrically grounded so that any charge pickup or induced currents are grounded.

In present methods and products for shielding windings, each particular winding is treated individually. Thus, a dielectric backing sheet is normally manually cut to a particular dimension and formed with a proper conductive foil in accordance with the specifications of a particular winding. The backing sheet is then wrapped about the winding, and a suitable ground connection effected with the foil strip. For another coil or different sized coil, the same process is repeated manually, the resulting shielding material having to be formed substantially completely by hand operation.

In most assembly and production operations, there are generally involved several hundred coils or windings of identical specifications, and the provision of individual shieldings for each of these coils by presnet methods can be extremely time consuming and costly. Further, since each coil or winding is individually treated, even though the windings may be of the same dimensions, there is no assurance of a uniform or consistent type of shielding. If the shielding is not of proper dimensions relative to the winding, short circuits can develop. In addition, in cutting the foil strip to be placed on the dielectric backing material to provide the shielded product, burrs are sometimes left on the cut edge; and such burrs on the foil strip may puncture the dielectric material, which material itself is extremely thin. This may result in what is known in the art as a high pot or weakened condition in the shielding means.

With the foregoing considerations in mind, it is a primary object of the present invention to provide a novel method and product for shielding windings where- 3,378,626- Patented Apr. 16, 1968 in the provision of the shielding material and the actual shielding operation can be carried out with a substantial reduction in the labor and time heretofore involved to produce equivalent shielded coils.

More particularly, it is an object to provide a novel method and product for shielding windings wherein consistency in the shielding of like windings is assured.

Another important object is to provide a novel method and product for shielding windings which will result in a more efiicient shielding of the windings and wherein the risks of shorting and high pots are substantially reduced.

Briefly, these and other objects and advantages of this invention are attained, in the preferred embodiments of the invention, by providing a dielectric backing sheet with a plurality of foil strips laminated on the sheet in spaced, parallel relationship. Suitable conductive wires are disposed alongside longitudinal edges of the strips, respectively. These wires serve ultimately as a means for grounding the foil strips; and towards this end, the wires are electrically connected to their associated strips.

By providing shielding material in the foregoing manner, a given longitudinal length of the backing sheet and strips may be cut transversely, and the resulting given length of material then wrapped about a plurality of winding groups simultaneously, such as provided on a stick core. There is thus involved only a single wrapping operation, and after the stick core winding groups have been wrapped, the stick core is cut between the winding groups to provide a plurality of separate windings, all properly and uniformly shielded.

The method and product also contemplates the provision of a pressure sensitive adhesive on the side of the dielectric backing sheet opposite that side to which the various foil strips are laminated. By the provision of such a pressure sensitive adhesive, the wrapping of the shielding material about the various windings is greatly facilitated.

After one or more windings have been wrapped and the windings separated as by cutting the stick core, a cut end of the conducting wire may be easily pulled out slightly or separated from the backing sheet to facilitate grounding of the foil.

The particular method of forming the shielding material will -assure uniformity in the wrapping or shielding of like windings. In addition, the dimensionng is such that more efiicient shielding is realized.

A better understanding of the method and product of this invention will now be had by referring to a specific example illustrated in the accompanying drawings, in which:

FIGURE 1 is a fragmentary schematic perspective view showing the formation of the shielding material in accordance with certain steps in the method of the invention;

FIGURE 2 is a fragmentary plan view of the resulting product;

FIGURE 3 is a cross section taken in the direction of the arrows 3-3 of FIGURE 2;

FIGURE 4 illustrates the step of wrapping a stick core having winding groups thereon in accordance with the method of the invention;

FIGURE 5 is a perspective view of a winding properly shielded in accordance with the present invention; and,

FIGURE 6 is a fragmentary cross section taken in the direction of the arrows 66 of FIGURE 5.

Referring first to FIGURE 1, there is illustrated one means for carrying out part of the method of the present invention for providing shielding material for windings. As shown, there is provided a roll 10 of a dielectric backing sheet 11 such as paper, polyester film, certain types of plastic film, or equivalent material. Also provided, as shown to the left of FIGURE 1, is a roll 12 of foil material 13 which may comprise copper, aluminum, or other electrically conducting film-like material.

Initially, the foil material 13 dispensed from the roll 12 is fed through a cutting apparatus comprising a shaft 14 mounting a plurality of cutting wheels 15. The cutting apparatus serves to cut the foil material 13 into a plurality of elongated strips such as indicated at 16, 17, 18, and 19 running generally in parallel, spaced relationship to each other. These strips are laminated onto the dielectric sheet 11 by passing the same through laminating rollers 20 and 21 which provide heat and pressure to bond the strips to the surface of the sheet.

Simultaneously with the bonding of the strips to the dielectric sheet, there are provided a plurality of conducting wires 22, 23, 24, and 25 passing from a guide roller 26 and supply spools 27, 28, 29, and 30, respectively. The conducting wires are caused to adhere to the sheet material 11 in positions alongside the strips 16, 17, 18, and 19, respectively.

Referring to FIGURE 2, there is shown in fragmentary plan view a small portion of the resulting shielding material provided from the apparatus of FIGURE 1. Ordinarily, the material will be rolled onto a take-up roll; and, in this respect, there may be provided several hundred feet of shielding material on a single roll.

In FIGURE 2, it will be noted that the various conducting wires 22, 23, 24, and 25 lie adjacent to one longitudinal edge of the various foil strips. In accordance with further steps in the method of shielding coils of this invention, a given length L of the shielding material is cut transversely such as along the section line 33. The length L is determined by the circumferential dimensions of a particular winding it is desired to shield.

After a given length has been severed from the material, the ends or other portions of the conducting wires 22-25 are respectively electrically connected to their corresponding adjacent foil strips. Such connection may be accomplished by effecting a solder joint as at 31 for the conducting wire 25 and adjacent foil strip 19 or, alternatively, by means of a conductive epoxy resin which is deposited to overlap the conducting wire and foil strip.

FIGURE 3 illustrates, with greatly exaggerated thickness dimensions being shown, the cross-sectional configuration of the shielding material taken in the direction of the arrows 3--3. In FIGURE 3, and in accordance with a further step of the method, the backing sheet 11 is shown provided with a pressure sensitive adhesive 32. In this respect, the dielectric sheet material 11 from the supply roll in FIGURE 1 may have the pressure sensitive adhesive coating applied by a process after the same has passed through the laminating rollers 20 and 21.

Referring to FIGURE 4, there is shown a stick core 33 supporting a. plurality of winding groups 34, 35, 36, and 37. In accordance with the invention, the shielding of these windings is effected simultaneously by wrapping around the winding groups the backing sheet with the foil strips as indicated by the arrow. The pressure sensitive I adhesive will cause the back of the dielectric sheet to adhere to the windings, and the dimensioning of the spaces between the elongated foil strips and the width of the strips themselves are such that the foil strips will overlie the respective coils. The length L for the particular stick core winding groups illustrated in FIGURE 4 is calculated such that there will result approximately a 25 percent overlap of the ends of the dielectric sheet material when the same is wrapped about the various windings.

After the shielding material has been wrapped about the windings of the stick core, and in accordance with a further step in the method, the shielding material and stick core are cut between the winding groups 34, 35, 36, and 37 such as at the gaps 38, 39, and 40. There thus results a plurality of individual windings, each of which is properly shielded.

FIGURE 5 shows the properly shielded winding group 37 severed from the remaining portion of the stick core 4 33. The spacing between the foil strips, such as the strips 18 and 19 in FIGURE 2, is such that when the cutting of the stick core takes place, there are provided marginal edges of the dielectric sheet material extending beyond either side of the longitudinal edges of the foil strip.

In FIGURE 5, it will be noted that there is an overlap of approximately 25 percent as described. Further, it will be noted that after the winding has been properly shielded, the conducting wire 25 may have its end portion 25' corresponding to the cut end lifted from the backing material into an accessible position for grounding so that the foil strip 19 can be conveniently grounded.

In the fragmentary cross section of FIGURE 6, it will be evident that the width of the foil strip 19 indicated at d corresponds to the actual width of the winding conductors, whereas the overall width D of the backing sheet corresponds substantially with the overall width of the winding itself. There thus results the marginal edge portions of width m on either side of the longitudinal edges of the foil 19 so that any possibility of short-circuiting between the foil 19 and any of the conductors in the winding 37 is avoided.

In the practice of the present invention, rolls of shielding material made up of a backing sheet with a plurality of elongated foil strips laminated thereon together with the conducting wires adjacent the various strips are sold as a bulk product to a user or manufacturing company. In this regard, the dimensions, such as the width of the foil strips, will be determined in advance for the particular coil windings to be shielded so that once a supply roll of .shielding material is provided the manufacturer, he can effect the shielding of a plurality of winding groups of like dimensions simultaneously as described in FIG- URE 4 in a very rapid and efficient manner, Further, each of the shieldings for the respective winding groups will be uniform.

The machine cutting of the foil into strips and the laminating of the same avoids burrs or other irregularities which might cause shorts or high pots.

In the event that a bobbin wound coil is to be shielded, the purchaser of the roll of shielding material may slit longitudinally the backing sheet between adjacent foils and employ single elongated strips of backing material and foil for the particular winding in question. Alternatively, the strips for 'bobbin windings may be supplied to the user by slitting the laminated structure in FIGURE 1 by a second set of cutters spaced properly to provide the proper margins between adjacent foil strips. The individual shielding strips are then wound on separate rollers and sold in bulk to the manufacturer or user.

It is also possible to provide shielding for torroidal windings wherein a second dielectric sheet is laminated onto the top surface of the foil strips and the conductive wires omitted. This operation may be readily effected by feeding in the second sheet between the rollers in FIG- URE 1 in lieu of the wires and then again slitting the laminated structure longitudinally by a second set of cutters. The resulting strips of foil sandwiched between the dielectric sheets may then be supplied on individual rolls to users or manufacturers of torroidal windings.

It should be understood from the foregoing that the method and product in their broadest aspects are not limited to the particular example set forth merely by way of illustration.

It will thus be evident that the present invention has provided a vastly improved method and product for facilitating the shielding of windings wherein the various objects set forth heretofore are fully realized.

What is claimed is:

1. A method of shielding windings comprising the steps of: providing a dielectric backing sheet with a plurality of foil strips running in spaced parallel relationship longitudinally along said sheet with conductive wires alongside one longitudinal edge of each strip respectively, said wires being electrically connected to their associated strip;

wrapping said backing sheet about winding groups spaced along a stick core; and cutting said backing sheet and stick core between said winding groups to provide a plurality of separate shielded windings.

2. The method of claim 1, including the step of providing a pressure sensitive adhesive on the side of said backing sheet opposite the side over which said foil strips extend.

3. A method of shielding windings comprising the steps of: cutting a sheet of conductive foil into elongated, parallel, spaced foil Strips; laminating said foil strips onto a dielectric backing sheet; adhering conductive wires to said backing sheet in positions alongside one longitudinal edge of each foil strip; transversely cutting said laminated strips, backing sheet, and wires to a given length; electrically connecting at least one end of each of said Wires to their adjacent foil strip; wrapping said backing sheet about winding groups spaced along a stick core such that said foil strips overlie said winding groups respectively with said backing sheet disposed between said foil strips and winding groups; cutting through said backing sheet and stick core between said Winding groups to provide separate shielded windings; and lifting from said backing sheet the cut end of the wire associated with the foil strip overlying a winding group preparatory to grounding of said wire and foil strip.

4. The method of claim 3, in which said wires are caused to adhere to said backing sheet simultaneously with the laminating of the associated foil strips to said backing sheet.

5. The method of claim 3, including the step of providing said backing sheet with a pressure sensitive adhesive on its backside opposite the side to which the foil 6 strips are laminated to cause said backing sheet to adhere to said winding groups during said wrapping step.

6. The method of claim 3, in which said given leng'h is such that said backing sheet is wrapped about said winding groups with approximately a 25 percent overlap.

7. A product for shielding windings comprising: an elongated backing sheet of dielectric material; a plurality of elongated fiat foil strips having widths correspondi g to the widths of the windings to be shielded laminated to one surface of said sheet in parallel spaced relationship to each other; and a plurality of conducting wires corresponding in number to the number of strips secured to said backing sheet in positions respectively alongside corresponding longitudinal edges of said foil strips and of a diameter substantially less than said widths whereby said backing sheets, strips, and wires may be cut transversely to provide desired lengths of said backing sheet and plurality of foil strips for wrapping about a plurality of winding groups on a stick core simultaneously.

8. A product according to claim 7, in which said backing sheet includes a pressure sensitive adhesive on its side opposite the side to which said foil strips are secured.

9. A product according to claim 7, in which the marginal longitudinal edges of said backing sheet extend beyond the longitudinal edges of the outer ones of said foil strips. i

References Cited UNITED STATES PATENTS 890,988 6/1908 Kitsee. 1,559,380 10/1925 Roe. 2,628,996 2/1953 Mayo W 17435 DARRELL L. CLAY, Primary Examiner. 

